1. Field of the Invention
The instant disclosure relates to a method of forming insolating structures; in particular, to a method for forming self-aligned isolation trenches in semiconductor substrate.
2. Description of Related Art
Dynamic random access memory (DRAM) is an electronic data storage device. In DRAM, each bit of binary data is stored in a tiny circuit called a memory cell consisting of a transistor and a capacitor. Generally, the better operating capability of computer software becomes, the greater memory capacitance of computer hardware need. Thus, the method for manufacturing DRAM capacitors is now an indispensable technology.
With the vigorous development of semiconductor industry, the dimension of integrated circuit elements nowadays range from micron size to submicron size. For DRAM, that is to say the cross-sectional area of each capacitor and each gap between capacitors become smaller. The traditional method for patterning the target layer on the substrate comprises the following steps. A photoresist material is spin-coated on the target layer in the first place. The photoresist material is exposed and developed through a patterned mask to form a patterned photoresist layer in the second place. Further, a process of etching is conducted to pattern the target layer by using the patterned photoresist layer as the etch mask.
However, in view of the resolution of pattern transfer is increased and the critical dimension of the line width is reduced. Limitation exists for improving lithography by only optical improvement.
In addition, MIM (Metal insulator Metal) capacitors basically a parasitic capacitor between the metal layers. Generally three or more reticles are used in the processing steps. In order to overcome its complex process, the design of DRAM will focus on a reduction in the number of reticles used.